A Review on Resistance of Antibiotics against Methicillin-Resistant

Staphylococcus aureus and effect of Curcumin on MRSA

V R Vishnu1, P K Vishal

1, B Arjun

1, Arya Rajendran

1, Asha Asokan Manakadan

2, T S Saranya*

2

1Student of B pharm, Amrita School of Pharmacy, Amrita Vishwa Vidyapeetham, Kochi, Kerala 2Department of Pharmaceutical Chemistry and Analysis, Amrita School of Pharmacy, Amrita Vishwa Vidyapeetham, Kochi, Kerala

Abstract

Antibiotics were ceaselessly used to treat bacterial infections and their constant use has developed high degree of resistance in bacteria.

Methicillin-resistant staphylococcus aureus (MRSA) is one among such potent bacteria that has been a great concern in almost all areas of

medicine. They almost halted the golden era of antibiotics. MRSA has been the reason for most of community acquired infections and hospital

acquired infections. The presence of a mutant in the bacteria makes it resistant against most of the antibiotics. Because of the lack of treatment

and expanded death rate there is a requirement for a potent therapy to convey an end to this bacterial infection.

Key Words- Curcumin, MRSA, Penicillin binding protein, Staphylococcus aureus, β-lactam antibiotics

INTRODUCTION

Methicillin-resistant Staphylococcus aureus is a gram positive

bacteria and an antibiotic resistant strain of staphylococcus

aureus. It has been found to be one of the reasons for nosocomial

infections. In 1972 it was from mastitic infected cattle MRSA was

first isolated. Animals and humans are mostly infected by these

bacteria. The infections include rashes, oesteomyelitus,

septicaemia and pneumonia [1]. This strain of S.aureus has

become a worldwide threat due to lack of treatment against this

bacteria. National nosocomial infection surveillance system shows

that S.aureus is the most common cause for nosocomial

pneumonia and one of the causes for bloodstream infections in

USA. In USA the mortality rate of different diseases like AIDS,

MRSA infection, hepatitis and tuberculosis were compared and

interestingly it was found that the mortality rate was found to be

more for MRSA infections. The prevalence rate for MRSA

infections in developed countries were found to be: UK (44%),

Japan (60-70%), USA (>50%) [2]. But 2011 reports shows that

the mortality rate in USA has declined due to proper hospital care

management. The bacterium is resistant to β- lactam antibiotics

like penicillin, methicillin, erythromycin etc. Their resistance to

antibiotics is due to the presence of mecA and mecC gene. MecA

gene plays a major role in the production of penicillin binding

protein 2a (PBP2a) [2]. PBPs are membrane bound enzymes that

helps in catalyzation of transpeptide reaction which is needed for

the cross-linkage of peptidoglycan chains. Due to low affinity of

PBPs to β-lactam antibiotics, Staphylococcus aureus can

withstand high concentrations of these antibiotics [3]. In some

MRSA strains the resistance is mainly influenced by a group of

genes called ‘blaz’. Another series of genes known as fem genes

also plays an essential role in resistance to methicillin by cross

linking peptidoglycan strands. The recent studies shows that the

MRSA were resistant towards methicillin (45.9%), cefixame

(44%), co-trimoxazole (28%), erthyromycin (28%), gentamycin

(18%). But 100% were sensitive to vancomycin (glycopeptide)

[2]. Need of discovery for new antibiotics become important when

vancomycin resistant MRSA was isolated in 1996 from Japan [1].

Linezolid is one of the synthetic antibiotics used recently for the

treatment. They act by destroying the bacterial growth by

inhibiting the initiation process in protein synthesis. Linezolid

also helps in inhibiting virulence factor expression and reduces

the amount of poison produced by gram positive pathogens.

Studies have shown that drugs against MRSA should be protein

synthesis inhibitors with a gram positive spectrum, eg:

quinupristin, dalfopristin [4]. Studies have shown that MRSA has

been acquired from hospital care workers who have poor

handwashing techinques. So these conditions can be minimised by

improving hand washing techniques. MRSA can be controlled by

identifying their colonies or the persons who are infected by it.

Active Detection and Isolation (ADI) (which include screening

high risk patients for MRSA, taking precaution for those who are

MRSA positive, adopting proper hand hygiene techniques) can be

used as a controlling technique for MRSA infections [5].

ANTIBIOTIC ACTION

The discovery of penicillin by Alexander Fleming opened the

door for other antibiotics to the world. Antibiotic used to treat

various diseases has specific site for its action [3]. In the recent

world majority of diseases has been cured with the antibiotics, this

lead to the detailed study about this class of drugs. They are

classified on the basis of mechanism of action, chemical structure,

or spectrum of activity. They act by inhibiting cell growth leading

to lysis of cell. Classification on the basis of mechanism of action

as follows:

Cell wall growth inhibitors

The following class of drugs acts by this mechanism: β-lactam

antibiotics, glycopeptides, bacitracin

a) β-lactam antibiotics

Eg: pencillins and cephalosporins

mechanism of action:

Major component of cell wall comprises of peptidoglycans [6].

The peptidoglycans are made of N-acetyl glucosamine and N-

acetyl muramic acid. The n-acetyl muramic acid unit contains

peptide chains which are the site of crosslinking. The S.aureus

contains pentapeptide chains of L-Ala-γ-D-Glu-L-Lys (Gly) 5-D-

Ala-D-Ala [7]. These are produced within the cell but the cross

linking takes place outside the cell. The cross linking is done by a

group of enzymes known as transpeptidases. These classes of

Enzymes are called Penicillin Binding Proteins (PBP).These are

bifunctional enzymes having both transpeptidase domain and

transglycosylase domain. The transglycosylase domain of the

enzyme helps in the extension of the sugar by the addition of new

peptidioglycan units from N-acetylglucosamine-b-1, 4-N-

acetylmuramyl-pentapeptide-pyrophosphoryl-undecaprenol [6].

The transpeptidases perform their activity by acylation using

serine as their active site [8]. The β-lactam antibiotics act on these

enzymes. They form covalent pencilloyl complex which prevents

the cross linking reactions and their by inhibiting the cell wall

synthesis.

b) glycopeptides

E.g : vancomycin,

Mechanism of action: It targets D-Ala-D-Ala terminal of cell wall

(peptidoglycan chain) inhibiting the transpeptidase activity. Thus

they prevent the cross linking of peptidoglycans which results in

poor cell wall synthesis. The resistance can arise by increasing the

thickness of cell wall. Vancomycin binds to the D-ala-D-ala

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terminal through five hydrogen bonds. This results in high affinity

of antibiotics to its target but production of D-ala-D-lac lead to

resistance against the site. c) bicitracin

They interfere with dephosphorylation of C55-isoprenyl

pyrophosphate which is a membrane carrier molecule that

transports the building blocks of bacterial cell wall [9]. It also acts

as a receptor in plasma membrane of bacteria.

NATURE OF RESISTANCE

Wide spread of MRSA has made an interest on identifying the

mechanism of resistance of S.aureus against different antibiotics.

It has been reported that most of the antibiotics used to treat

MRSA have acquired resistance against its action. β– lactam

antibiotics which have greater onset of action against the infection

and so this class of drugs (penicillin, erythromycin) was used.

Methicillin is no longer used due to its nephrotoxicity, yet the

Staphylococcus aureus resistant to cloxacillin or nafcillin are

refered as methicillin resistant organism. The action of β–lactam

antibiotics is due to the presence of Penicillin Binding Protein

(PBP) in the cell wall of bacteria which have affinity over β–

lactam antibiotics covalently [8]. The key role of β–lactam

antibiotics is that it acts as substrate analogues for PBPs which

helps in catalyzing transpeptidation. Most commonly the

resistance is introduced by the production of enzymes which alters

the antibiotic structure [10]. Most of the clinically obtained

MRSA contain a staphylococcal origin gene mecA coding 78kd

PBP2a having affinity towards β-lactam ring [11]. General

assumption has made that mecA gene act as surrogate enzyme for

synthesis of cell wall. MecA gene have structural resemblance of

cell wall synthesizing transpeptidase. This mecA gene can easily

transfer fron one to other S. aureus [12]. A bacterial cell wall is

composed of repeating units of disaccharides which include N-

acetyl glucosamine and N- acetyl muramic acid. The N-acetyl

muramic acid is modified by pentapeptides which is one of the

differentiating factor in gram positive and gram negative bacteria.

The peptidoglycan is produced inside the cell but their

crosslinking takes place outside the cell membrane.

Transpeptidases are the enzymes which does this function. After

the cross-linking a peptide bond is formed between D-alanine

group of one chain with the L-lysine group of the other.

Transpeptidases enzyme uses an active serine and performs their

function by acylation. This is the site where β-lactam antibiotics

act to produce their effect. They inhibit the transpeptidases

enzyme thereby preventing the cross-linking of peptidoglycans.

The transpeptidase enzyme forms a strong covalent bond with the

antibiotics and thereby prevents the further reactions. Since the

S.aureus has attained resistance over this mechanism mecA gene

takes over the step of cell wall synthesis. This leads to the

investigation for other site to fight against the resistance.

MECHANISM OF RESISTANCE

The bacterial cells produce resistance against antibiotics by three

mechanisms:

Preventing the antibiotic attack to the target site by

mechanism of altered permeability(via efflux pumps)

By transforming the target site

By the inactivation of antibiotics (by enzymes) [13]

1. Enzymatic action:

The β-lactamses classes of enzymes are responsible for this

activity. They are also called as pencillinase or cephalosporinase.

Penicillinase is mostly active against penicillin whereas

cephalosporinase are active against cephalosporins. Sometimes

both types are present in the same organism. It is one of the

defense mechanism against antibiotics in gram negative bacteria.

β-lactamases cleaves the β-lactam ring of pencillin and other

antibiotics [3]. They are classified into four classes (A to D). They

all have mechanism that involves the nucleopilic attack of β-

lactam antibiotics on the active site serine which results in acyl-

enzyme intermediate [8]. This is a type of nucleophilic

substitution reaction in which β-lactam ring act as a nucleophile.

This intermediate is hydrolyzed by base activated water molecule.

Generally β-lactamases inhibitors are given in combination with

β-lactam antibiotics to counteract this resistance.

Extended spectrum β-lactamases (ESBLs) intercede protection

from all pencillins, third generation cephalosporins. They are for

the most part distinguished in E.coli yet additionally have been

found in enterobacteriaceae. [13]

2. Target alteration:

The second mechanism includes target modification so that the

antibiotic can’t bind legitimately. Due to the imperative cell

elements of the objective locales, creatures can’t sidestep

antimicrobial activity by abstaining from them completely.

Generally the target for β-lactam antibiotics is to inhibit cell wall

synthesis. This is achieved by their capacity to bind covalently

with radiolabelled penicillin. These proteins to which antibiotics

(β-lactam antibiotics) bind are called Pencillin Binding Protein

(PBP). A given life form contains four to eight PBPs with sub-

atomic sizes of 35 to 120 kDa. There is no fundamental

connection between identically numbered PBPs of two random

organisms, although taxonomically related organisms have

comparable PBPs. There are two types of PBPs in an organism

based on their molecular weight- Low molecular weight and high

molecular weight PBP [14]. Most of the microorganisms are

resistant to penicillins because of the alteration of PBPs. This

alteration mostly occurs due to procured mutation or due to any

chromosomal facto r exchange. Resistance to macrolides is due to

the attainment of one of 21 erm genes. These genes codes for

rRNA methylases which are the enzymes for the addition of a

methyl group on adenine residues in 23s rRNA. These inhibits the

binding of macrolides to 50s ribosomal subunit [5]. PBP2a belong

to the class of high molecular weight PBPs. Most of the PBPs

have high transpeptidase activity which is required for the

crosslinking of membranes proteins. This transpeptidase activity

of PBPS has been inhibited by methicillin but they were not able

to inhibit PBP2a because they largely depend on transglycosylase

activity.

PBP2a is encoded by a mecA gene which is present at the 30kb

DNA segment. These are present in the chromosome of MRSA.

This is an additional gene present in MRSA which are found to be

absent in MSSA (methicillin susceptible Staphylococcus aureus).

Vancomycin was one of the important drugs which were used for

the treatment against MRSA infections, but unfortunately in the

last few years MRSA has acquired resistance against vancomycin.

This is due to presence of van A which caused alteration in the

vancomycin binding site. It is accompanied with three fold

increase in the production PBP2a and PBP2’. Similarly most of

the drugs including oxacillin became ineffective due to the

presence of PBP2a [4]. Their major fuction is to provide the

transpeptidase and transglycosylase activity which are important

for the cross-linking of cell wall. These are inhibited by β-lactam

antibiotics in susceptible species.

The other target alterations include alteration in protein synthesis,

alteration DNA synthesis. The mechanism of action of macrolides

and lincosamide is different from that of β-lactam antibiotics.

They inhibit the protein synthesis by binding with 50s ribosomal

subunit. But MRSA shows resistance toward macrolides and

lincosamide by the alteration in 23s ribosomal component of 50s

ribosomal subunit. These occurs during the post transcriptional

period where the 23s rRNA component get altered and therefore

the macrolides cannot bind to the 50s subunit. The drugs which

act by inhibiting the dna replication and transcription are the

quinolines especially fluoroquiolines. They mainly inhibit the dna

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gyrase and topoisomerase enzymes. The resisitance to quinolines

in mrsa occurs by mutation in the structural gene which alters

both the enzymes. This reduces the affinity of enzymes to

quinolines [3].

3. preventing the antibiotic attack to the target site (efflux

pumps)

A drug has to reach its specific target to produce its therapeutic

action. Drug resistance can be acquired by preventing the

antibiotic from reaching its target site. This can be achieved by

means of efflux pumps. Efflux pumps are membrane proteins that

export antibiotics out of the cell. A drug concentration inside the

cell depends on its permeability through the cell membrane.

Resistance to penicillin in gram negative bacteria occurs mainly

by this mechanism. The outer membrane of bacteria contains

aqueous channels formed by proteins called porins which allows

the rapid entry of most of the antibiotics. Mutations in the gene

coding for porins can prevent the entry antibiotics into the cell.

Efflux pumps are one of the important systems which are involved

in the expulsion of tetracycline from the cell [14]. It is one of the

most identified and studied mechanism by which tetracycline

resistance is caused. The tetracycline accumulation in bacteria is

related with energy supplied in the cell. The studies have shown

that tetracycline expelled out of the cell in presence of energy and

its accumulation increases when energy is not supplied. This was

carried out by specific proteins present in the outer membrane

called tet protein. The efflux system by the tet protein is indeed a

antiport system which export one molecule of tetracycline out of

the cell for one proton which is entering into the cell. Efflux

pumps may be of single or multi component pumps. The presence

of multi drug efflux pumps is the reason for multi-drug resistance

in most of the bacteria. Efflux pumps are regulated by specific

genes which can themselves be a target for the antibacterial

agents. They are mostly regulated by global receptors which

include marA, soxS, rob. They are also regulated by two

component system. Any mutations in these genes can reduce the

resistance and therefore it increases the susceptibility of

organisms to antibiotics. Efflux inhibitors can be used for this

purpose [13].

ANTI-BACTERIAL EFFECT OF CURCUMIN AGAINST

METHICILLIN RESSISTANT STAPHYLOCOCCUS

AUREUS

MRSA (Methicillin-Resistant Staphylococcus aureus) is a rapidly

spreading infectious disease and their ability of high resistance to

antibiotics lead to some serious provocations regarding the

treatment of this disease [15]. Curcuma longa a herbaceous

rhizome have many actions in human body. It is native to India

and south Asian countries. Major constituent curcumin has several

properties like anti-bacterial, anti-inflammatory, antioxidant and

anti-amyloid activities [16]. It has less repercussion in pregnancy

and lactation period [17]. The major constituent curcumin has

exhibited a wide range of pharmacological action at low doses

[18]. At higher doses curcumin shows genotoxicity. Curcumin is

extracted from turmeric by solvent extraction with the help of

various methods such as Soxhlet, microwave etc [18]. Curcumins

antibacterial activity was tested against the strains of MRSA by

combining with other antibiotics such as oxacillin, ampicillin and

norfloxacin showed positive results by reducing the minimum

inhibitory concentration of the drug thus reducing the bacterial

count to a high extent [15]. A standard broth micro dilution

method was used here. Curcumin were prepared in MHB in sterile

conditions [15]. A checker board test was done to evaluate two or

more drug combinations and respective assays were performed

with OXI, AMP, CIP and NOR. Interactions between the in vitro

drugs were determined by the fractional inhibitory concentration

or (FIC) index [15].

FIC index = FICa + FICb = [A]/MICa + [B]/MICb where,

[A]=CONCENTRATION OF DRUG A

[B]=CONCENTRATION OF DRUG B

FIC and MIC are the respected minimum inhibitory concentratiom

values for drugs A and B [15]. In a research MIC calculated

through computational studies shows that curcumin conjugated

chitosan microspheres has more action against S. aureus than

curcumin alone [19].

The cheker board broth method provided more precise results and

suitable for studies with multiple concentration of compounds.

The main mechanism behind curcumin is able to reverse the

resistance when used in combination with other drugs [18].

Disadvantage of curcumins

There are also certain things which challenge the use of curcumin

as an antibiotic which mainly include evidences of cytotoxcicity.

Another one includes the ability to promote lung cancer. It is

linked to the induction of reactive oxygen species (ROS) such as

hydrogen peroxide [18]. Nausea, diarrhea and increased serum

alkaline phosphatase are one of the major after impact. In addition

to this curcumin has poor solubility and low bioavailability due to

rapid metabolism by sulphation, methylation and glucaronidation

[20]. In presence of detoxifying enzymes curcumin will get

degraded rapidly. But studies have also shown that the products

obtained from degradation of curcumin is mainly responsible for

the pharmacological actions [18]. Curcumin treatment may cause

growths despite the anticancer activity of curcumin is very much

archived. As curcumin is an effective iron chelator, it might

conceivably influence fundamental iron digestion particularly the

individuals who have problematic iron status. Moreover curcumin

has been accounted for to hinder the compounds that use

medications, such as cytochrome p450s. This may prompt the

aggregation of non metabolized medicates in blood and ends up

causing toxicity [18]. Notwithstanding potential danger, poor

solvency, and low boo availability, curcumin experiences several

difficulties when it is regulated either through oral or intra venous

course because of the idea of body frame work. A lot of curcumin

may get corrupted within the sight of detoxifying and metabolic

compounds, or it might tie to the circulatory proteins, for

example, egg white which may possibly diminish its action [18].

Resistance

Curcumin has demonstrated powerful antibacterial action and

other pharmacological activities in the past few years [15].

Curcumin has been showcased all around as a well being

supplement essential for its cell reinforcements and calming

properties. Likewise, it additionally can possibly be created into a

anti-toxin against Methicillin-Resistant Staphylococcus Aureus

and other bacterial strains later on.

ANTIBIOTIC COMBINATIONS AGAINST MRSA

Methicillin-Resistant Staphylococcus aureus (MRSA) is a

considerable general medical issue around the world, causing

huge dreariness and mortality and raised medicinal services costs.

There were an expected 94360 obtrusive MRSA contaminations

in the United States in 2005, causing more than 18 000 passing’s

for every year. Methicillin-Resistant S. aureus pervasiveness has

expanded in the course of the most recent 10 years; MRSA-related

doctor's facility releases have multiplied more than 10 years, with

doctor's facility releases for MRSA skin and delicate tissue

contamination tripling since 2004.Infections caused by MRSA are

related with longer healing center stays and an expanded

budgetary weight on society, costing an expected US $14.5 billion

for all inpatient days in 2003.An case of the expanded grimness

and mortality related with MRSA can be seen when contrasting

the yearly disease rates and death rates in the United States for

MRSA, AIDS, viral hepatitis, and tuberculosis. Methicillin-

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Resistant S aureus is evaluated to cause a larger number of

contaminations than alternate maladies consolidated and a bigger

number of passings every year than AIDS [1].

Β- LACTAM BINDING ACTION, A DETAILED STUDY

A vast assortment of anti-microbial blends are of now being used

against MRSA contaminations the vast majority of the anti-

microbial mixes act synergically and is bactericidal against

MRSA. Drugs, for example, vancomycin and linezolid are the

most broadly utilized. Twofold blends, for example, vancomycin

with imipenem and fosfomycin with cetazolin were utilized

however wound up as disappointments. Most antimicrobial

operators utilized for the treatment of bacterial contaminations

might be sorted concurring their important system of activity.

There are four major route of actions [3]. (1) impedance with cell

divider synthesis,(2) restraint of protein blend, (3) interference

with nucleic corrosive union, (4) hindrance of a metabolic

pathway [13]. The effectiveness of β-lactam antibiotic depend on

their ability to form covalent linkage with target site [21].

Antibacterial medications that work by repressing microscopic

organisms cell divider blend incorporate the b-lactams, for

example, the penicillins, cephalosporins, carbapenems, and

monobactams, and the glycopeptides, including vancomycin and

teicoplanin [8].

PBPs are characterized as those bacterial proteins that

predicament penicillins and other fJ-lactam anti-infection agents

covalently. PBPs are promptly distinguished and their relative

sums quantitated by brooding of bacterial films with [14C]

penicillin G, trailed by sodium dodecylsulfate (SDS) gel

electrophoresis and ftuorography [5]. The liking of a PBP for

guaranteed (non-radio labeled) fJ-lactam is normally

communicated as the grouping of anti-microbial required to lessen

[14C]penicillin-G authoritative to the PBP by half and is resolved

after preincubation with the unlabeled fJ-lactam under given states

of time, temperature [5]. Studies went for reasoning which PBPs

are deadly focuses for f3-lactam anti-microbial have used two key

methodologies: examination of mutants with adjusted PBP

examples and relationships between's in vivo and in vitro impacts

of fJ-lactams. In this manner, the physiological results of

inactivation of specific PBPs, either by change or by treatment

with exceptionally particular fJ-lactams, have been inspected and

the in vivo elements of the PBPs inferred [5]. β-Lactam specialists

restrain synthesis of the bacterial cell divider by meddling with

the compounds required for the blend of the peptidoglycan layer.

Vancomycin and teicoplanin additionally meddle with cell divider

amalgamation, yet do as such by official to the terminal D-alanine

buildups of the incipient peptidoglycan chain, along these lines

keeping the cross-connecting steps required for stable cell divider

synthesis [13]. Notwithstanding penicillins and cephalosporins,

the vancomycin group of glycopeptide anti-microbials

additionally focuses on the cell forming peptidoglycans. But

instead than focusing on the catalysts engaged with peptide

crosslinking, vancomycin ties up the peptide substrate and in this

manner keeps it from responding with one of the transpeptidases

or transglycosylases. The net impact is the same: inability to make

crosslinking of peptidoglycans prompts a weaker divider that

inclines the treated microbes to a lysis of the cell wall layer. The

container molded base of the vancomycin anti-infection makes

five hydrogen bonds to the D-Ala-D-Ala dipeptide end of each

uncrosslinked peptidoglycan pentapeptide side chain, which

represents the high fondness of the anti-microbial for its objective,

both in halfway crosslinked dividers and in the lipid II middle of

the road. Since β-lactams and vancomycin chip away at

contiguous advances - substrate and catalyst , they indicate

cooperative energy when utilized as a part of combination [4]. For

anti-microbials to be compelling they should achieve their

particular bacterial targets and collect at fixations that can

demonstration in some sensible time period. For instance, the

protein-amalgamation hardware is situated in the cytoplasm so

antibacterials that are inhibitors of protein union must go through

the cell films (external andinner porousness obstructions for

Gram-negative microscopic organisms; internal layer hindrances

for Gram-positive microbes) and after that collect to a sufficiently

high focus to hinder the specific vulnerability advance of protein

get together. Both Gram-positive and Gram-negative microscopic

organisms that wind up plainly impervious to antibiotic

medications generally overproduce related film proteins (with

relative sub-atomic masses of 42,000) that go about as a fare or

efflux pump for the drug [4].

A structural representation of penicillin binding protein from

Staphylococcus aureus is shown below. It shows penicillin like

antibiotic binding site, non active sites and transpeptidase region

(domain which is responsible for the synthesis of cell wall in

bacteria).

--

Fig: 1 Structure of penicillin binding protein 2A from

Methicillin-Resistant Staphylococcus aureus strain 27R showing

the β-lactam binding site, non active region and transpeptidase

area.

DRUGS AND COMBINATIONS

Tetarimycin A, Tetarimycin A (1) is an anti-infection with

movement against methicillin-resistant Staphylococcus aureus

(MRSA) identified through Induced Expression of Environmental

DNA Gene Clusters [22]. It is gram positive particular anti-

microbial with strong action, The structures of 1 and a noteworthy

dormant metabolite, tetarimycin B, were illustrated utilizing a mix

of high-determination mass spectrometry (HRMS) and NMR

information . The structure (1) was additionally accordingly

affirmed by single-precious stone X-beam diffraction analysis

(information from which were kept with the Cambridge

Crystallographic Data Center under promotion number CCDC.

The two mixes are novel tetracyclicnatural products [22].

Synergism of vancomycin with other antibiotics

Vancomycin is regularly joined with a moment anti-microbial,

frequently rifampin or gentamicin, for the mitigation of genuine

methicillin-resistant staphylococcus aureus infections [23].

Theoretical explanations behind the utilization of anti-infection

agents in mix with vancomycin for the treatment of genuine

methicillin-resistant S. aureus (MRSA) contamination incorporate

the accompanying:

To widen scope to incorporate VISA and heteroresistant VISA

and to enhance action against secludes with a base inhibitory

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focus (MIC) at or drawing nearer the breakpoint for

powerlessness

To keep the development of decreased vulnerability to

vancomycin

To give movement against stationary-stage life forms and

creatures developing in biofilm

To enter cells and tissues not came to by vancomycin [23].

Vancomycin in addition with rifampin and gentamicin, relevant

procedures for the treatment of prosthetic valve endocarditis

(PVE) caused by MRSA suggest the utilization of the 3-medicate

mix of vancomycin, rifampin, and gentamicin, with the

aminoglycoside controlled for just the initial 2 weeks of treatment

. Interestingly, the rules don't prescribe the expansion of rifampin

to vancomycin for the treatment of native valve endocarditis

because of MRSA. The proposal for the 3-medicate blend in the

treatment for MRSA. PVE has all the earmarks of being an

extrapolation from the suggestion for the treatment of PVE

because of S. epidermidis , which, evidently, is prevalently in

view of a review investigation of an aggregate of 26 patients

getting different regimens, with or without attendant surgical

treatment . In that review, 19 of the 26 patients got consolidated

medicinal and surgical treatment, leaving 7 for whom anti-toxin

treatment was assessable just 1 of whom got vancomycin

monotherapy [23]. Nisin, an antibacterial substance delivered by

Lactococcuslactis (once in the past Streptococcus lactis,

Lancefield bunch N), found over 80 years back, is generally

utilized as a sustenance additive. It is viewed as a bacteriocin,

however is atypical in having a wide range of movement against

Gram-positive bacteria.1 Nisin is a polypeptide containing 34

amino corrosive deposits (mol. wt 3353), including the strange

mixes lanthionine and β-methyllanthionine: therefore it isclassed

as a 'lantibiotic is additionally used to treat MRSA [24].

The in vitro action of the oxazolidinone linezolid was

contemplated alone and in mix with three anti-microbials

following up on various cell targets. Oxazolidinones are bacterial

protein amalgamation inhibitors that demonstration at a beginning

time by keeping the arrangement of the start complex. Mixes of

linezolid with gentamicin, vancomycin or rifampicin were

assessed against for methicillin-resistant Staphylococcus aureus

strains, utilizing murdering bends in conjunction with examining

electron microscopy. Linezolid in addition to rifampicin had all

the earmarks of being the most dynamic mix against methicillin-

resistant S. aureus strains in time– kill experiments [25].

NEW TREATMENT APPROACHES AND THERAPEUTIC

ALTERNATIVES

In the recent time it has been said that MRSA infections in the

western countries like America has increased and mortality rate is

increased than the AIDS. Life threatening diseases are caused by

toxins from CA-MRSA strain like Panton- Valentine Leukocidin

(PVL) and Phenol-Soluble Modulins (PSM) [26]. About three half

of the infection affects skin and soft tissues in the body. There are

several drugs which were introduced into the action and were got

resisted. A phage therapy was also experimented. There are some

conditions to be fulfilled for getting an effective antibiotic like

antibiotic target must exist inside the bacterial cell, effective

amount of antibiotic must be reached in targeted site, the

antibiotic should not get metabolized. Introduction of third

generation cephalosporins shows a wide coverage using a single

therapeutic agent. Number of studies has shown that monotherapy

is better than combination therapy Daptomycin, a cyclic

lipopeptide antibiotic was used to treat both CA-MRSA and HA-

MRSA. It acts by disrupting the bacterial cell wall leading to its

lysis. It was accepted due to its safe line but it got inactivated by

pulmonary surfactants. Vancomycin was used to overcome the

infection. It was selected due to its safe profile and insufficient

active drug. Use of this was stopped due to the evolution of

Vancomycin Intermediate Resistant Staphylococcus aureus

(VISA). Methanolic extract of Samadera indica have good

bactericidal activity against S. aureus [27]. Chemotherapy using

linezolid was limited due to its expenses. There several antibiotics

like glycylcycline antibiotic, cephalosporins (due to its affinity on

PBPs) were used [28]. There are several researches undergoing to

develop new drugs with a novel action against MRSA.

Development of novel drugs should be able to overcome the

resistance offered and its actions should involve shortening the

therapy schedule, harmful effects should be reduced or eradicated,

moreover the resistance should be eradicated and the combination

therapies must have excellent efficacy. A research has been done

to find the anti-inflammatory activity of Mirabilis jalapa Linn.

and found that alcoholic and petroleum ether extract show good

anti-inflammatory action [28]. Contemporary details of the

research can be sited in several web sites. Some of the recent

studies in MRSA had came out and several industries are working

to get a result. Some of the studies and inventions of different

companies are mentioned below :

Table contains array of drugs and their method of inhibition.

Some of them are under clinical studies.

Table: 1 showing antibacterial agents with their mode of action

and some compounds under clinical trials by several industries

[28].

Drug Mode of action

Oritavancin Inhibition of peptidoglycan biosynthesis

Dalbavancin Inhibition of peptidoglycan biosynthesis

(lipoglycopeptide)

TD-1792 Inhibition of peptidoglycan biosynthesis

Mupirocin Inhibition of bacterial protein synthesis by

inhibiting isoleucyl tRNA synthase

Iclaprin Inhibition of dihydrofolate reductase

XF-73 Depolarization of cytoplasmic membrane

TP-434 Inhibition of bacterial protein synthesis by

targeting ribosome

BC-3781 Inhibition of protein synthesis by targeting 50S

ribosomal subunit

BC-7013 Inhibition of protein synthesis by targeting 50S

ribosomal subunit

BC-3205 Inhibition of protein synthesis by targeting 50S

ribosomal subunit

RX-1741 Inhibition of protein synthesis by targeting 50S

ribosomal subunit

Tedizolid Inhibition of protein synthesis by targeting 50S

ribosomal subunit

Tomopenem Inhibition of bacterial cell wall synthesis by

binding to penicillin binding protein

Cethromycin Inhibition of protein synthesis by targeting 50S

ribosomal subunit

NX-103 Inhibition of protein synthesis by targeting

ribosomal subunit (synergistic effect)

Delafloxacin Inhibition of bacterial gyrase

LBM-415 Inhibition of bacterial protein synthesis by

inhibiting peptide deformylase

GSK1322322 Inhibition of bacterial protein synthesis by

inhibiting peptide deformylase

MSI-78

Formation of an amphipathic α-helical peptide

on membranes that induces pore or changes

membrane permeability

OligoG CF-

5/20 Immunomodulating activity

F598 Inhibition of virulence by targeting the PNAG

carbohydrate of the bacterial capsule.

V R Vishnu et al /J. Pharm. Sci. & Res. Vol. 10(5), 2018, 1198-1203

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CONCLUSION

The era of antibiotic dominance has been coming to extinct after

the brunt of bacteria against antibacterials. Growing infections are

impossible to treat and leads to severe health care risks. WHO

mentioned that newly discovered agents are not effective against

highly resistant bacteria. Most of the phyto constituents are having

effective antibacterial effect but the technique of isolation and

search should be systematically done to get a proper effective

antibiotic with safer margin of action. Since the present antibiotics

are resisted in action, novelty of new antimicrobial must

overcome it.

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